Linux - LXDE -- setting default browser will not stick

OS=Debian stretch, running LXDE

Clicking on URL links from within non-browser programs, such as pidgin or Thunderbird does not open the links. I discovered that the default browser is set to thunderbird.desktop ... very odd... don't ask me how that got set.

$ xdg-settings get default-web-browser
thunderbird.desktop

Trying to set the default browser with xdg-settings does not work:

xdg-settings set default-web-browser firefox-esr.desktop
$ xdg-settings get default-web-browser
thunderbird.desktop

Interestingly update-alternatives --get-selections shows firefox-esr as the default browser.

$ update-alternatives --get-selections |grep browser
gnome-www-browser auto /usr/bin/firefox-esr
infobrowser auto /usr/bin/info
www-browser auto /usr/bin/w3m
x-www-browser auto /usr/bin/firefox-esr

I also tried an entry in ~/.local/share/applications/defaults.list

$ cat ~/.local/share/applications/defaults.list
text/html=firefox-esr.desktop;

Nothing is working. Any help appreciated.

Update:

These lines in ~/.config/mimeapps.list were set to thunderbird.desktop. I changed them to firefox-esr.desktop, but still no change.

application/x-extension-htm=firefox-esr.desktop
application/x-extension-html=firefox-esr.desktop
application/x-extension-shtml=firefox-esr.desktop
application/xhtml+xml=firefox-esr.desktop
application/x-extension-xhtml=firefox-esr.desktop
application/x-extension-xht=firefox-esr.desktop

Update:

The command xdg-mime query filetype index.html comes back empty. In fact it comes back empty with other filetypes as well. This has to mean something. However mimetype works.

$ mimetype index.html
index.html: text/html

[SOLVED] as per Xen2050's answer

Here is a summary of what I did, in case others have a similar problem:

I had to find all ''mimeapps.list'' and ''defaults.list'' files:

locate mimeapps.list
locate defaults.list

Then delete them...

rm ~/.config/mimeapps.list
...

Then run:

update-desktop-database

In my case I got an error message about a faulty mime-type with evince (sorry, can't remember the exact message). So i purged evince:

apt-get purge evince
apt-get purge thunderbird #just for good measure

Try again:

update-desktop-database

The problem was still not solved, so I went on to install ''exo-preferred-applications'', which in Debian is the package ''exo-utils''. Then reinstall thunderbird. I don't need evince so didn't reinstall it.

apt-get install exo-utils
apt-get install thunderbird

Then ran ''exo-preferred-applications''. Firefox was not listed under "Web Browsers", so I chose ''other'' and pasted in ''firefox-esr.desktop''. Then ran:

update-desktop-database

Working!!!:

$ xdg-mime query default x-scheme-handler/http
firefox-esr.desktop
$ xdg-mime query default x-scheme-handler/https
firefox-esr.desktop

The original problem of clicking on links in non-browser applications is also now solved.

3 Answers

The GUI's "Settings" -> "Preferred applications" looks like it sets xdg-settings get default-web-browser also, perhaps differently and definitely with an easier interface, so try there.

• It looks like it runs exo-preferred-applications
• Might rely on the file /usr/share/applications/exo-web-browser.desktop (or corresponding file in /usr/local/ or ~/.local) containing Exec=exo-open --launch WebBrowser %u

Also try

sudo update-alternatives --config x-www-browser

Also, checking the default mimetypes command you were looking for was probably one of these:

xdg-mime query default x-scheme-handler/http
xdg-mime query default x-scheme-handler/https

If MIME types were changed, the command [sudo] update-desktop-database might help.

• More info on mimetypes & file associations:

Problem already known in Debian GNU/Linux 8 alias Jessie. No matter whether you LXDE or Gnome. :-(

Here ist the Evince error message:

~$ sudo update-desktop-database

Error in file "/usr/share/applications/evince.desktop": "" is an invalid MIME type ("" does not contain a subtype)

I purged evince. Not needed, too...

My System:

~$ uname -a

Linux 4.9.0-11-amd64 #1 SMP Debian 4.9.189-3 (2019-09-02) x86_64 GNU/Linux

For what it's worth: I've also just faced this problem, and solved it by overriding, as user root, /usr/share/applications/mimeinfo.cache with the appropriate values for x-sceheme-handler/http, etc.

For some reason it seems that this file takes precedence over any local, user-writable files.